Endocrine disrupting chemicals (EDCs) are substances that can mimic or alter the function of hormones in the body. Previous studies have mostly used cell culture to examine EDCs effects on specific hormone responses. We propose to use transgenic zebrafish allowing direct examination of subtle alterations in endocrine organs and hormone responses in living animals to analyze the cellular behavior and gene expression changes that occur following exposure to EDCs. These transgenic zebrafish have the green fluorescent protein (GFP) reporter gene expressed, respectively, in pancreas directed by the insulin promoter, in pituitary by the POMC promoter, and all cells that respond to estrogens by the vitellogenin B1 promoter. Flow cytometry and gene expression analysis by microarrays and microSAGE will be used to provide a profile of the genes activated by EDCs at the cellular level. Cytokines, chemokines, signal transduction messengers, proteases, oncogenes or cell cycle-related products will be the focus studied in the separated GFP-expressing cells and compared between the natural estrogen exposure and xenoestrogen exposure groups. To generate more tools to study endocrine organ development and EDC induced responses, we will also perform a large-scale chemical compound screen using the transgenic embryos from each line. Small molecules that have specific effect in either endocrine cell lineage development or estrogen responses will be selected for future studies. Due to the high conservation of the biological processes to be studied in this proposal, we believe that findings from zebrafish should ultimately help us understand how environmental stresses exert their impact on the human endocrine cell development and responses. [unreadable] [unreadable]